The Effect of Calcium on the Fluidity and Phase Properties of Microsomal Membranes Isolated from Postclimacteric Golden Delicious Apples

スポンサーリンク

概要

• 論文の詳細を見る

• Calcium and magnesium have been found to stabilize and preserve the ethylene-synthesizing capacity of postclimacteric Golden Delicious apple slices. In order to assess if this reflects an effect at the membrane level, we have used three spin labels to assay changes in the physical properties of isolated microsomal membranes treated with calcium. A surface spin label, 18NP (an 18 carbon alkane with a terminal quaternary amine attached to a nitroxyl-containing pyrollidine ring), reported a 20.8% increase in rotational correlation time (τc) at 25℃ and a 25.3% increase in activation energy (Ea) calculated from linear Arrhenius plots of τc for microsomal membranes treated with 50 m_M CaCl_2. Regions deeper within the bilayer were probed using two fatty acid spin labels-1(12,3), stearic acid bearing a paramagnetic nitroxide group on carbon 5, and I(1,14), stearic acid bearing a paramagnetic nitroxide group on carbon 16. The calcium effect was less pronounced deeper within the lipid bilayer, there being only a 10.6% increase in τc and a 6% increase in the value of an order parameter (S) calculated from spectra recorded at 25℃ for microsomes treated with 50 m_M CaCl_2 and labelled with I(1,14) and I(12,3) respectively. There was no significant change in Ea for I(1,14)-labelled membranes treated with 50 m_M CaCl_2. Similar trends were observed for membranes treated with 5 m_M CaCl_2, although the degree of change was less and differences were not always significant. Wide-angle X-ray diffraction revealed that untreated microsomal membranes from postclimacteric apples were exclusively liquid-crystalline at 25℃, as were microsomes treated with 50 m_M CaCl_2. The transition temperature, defined as the highest temperature at which gel phase lipid could be detected, was below -25℃ for both treated and untreated membranes. It is apparent, therefore, that Ca^<2+> rigidifies and stabilizes membranes, particularly at their surfaces. Inasmuch as parts of the ethylene biosynthetic pathway appear to be membrane-associated, this rigidification may, in part, act to preserve ethylene production.

• 日本植物生理学会の論文

著者

• Thompson J.E.

  Department of Biology, University of Waterloo

• Thompson J.e.

  Department Of Biology University Of Waterloo

• Thompson J.e.

  Department Of Biology University Of Walerloo

• Legge Raymond

  Department of Biology, University of Waterloo

• Baker J.E

  Postharvest Plant Physiology Laboratory, Beltsville Agricultural Research Center

• Lieberman M.

  Postharvest Plant Physiology Laboratory, Beltsville Agricultural Research Center

• Baker J.e

  Postharvest Plant Physiology Laboratory Beltsville Agricultural Research Center

• Lieberman M.

  Postharvest Plant Physiology Laboratory Beltsville Agricultural Research Center

• Legge Raymond

  Department Of Biology University Of Waterloo

関連論文

• Effects of Cytokinins and Antioxidants on the Susceptibility of Membranes to Ozone Damage
• Free Radical-mediated Formation of Ethylene from 1-Aminocyclopropane-1-carboxylic Acid : A Spin-trap Study
• Evidence for Involvement of the Superoxide Radical in the Conversion of 1-Aminocyclopropane-1-Carboxylic Acid to Ethylene by Pea Microsomal Membranes
• The Effect of Calcium on the Fluidity and Phase Properties of Microsomal Membranes Isolated from Postclimacteric Golden Delicious Apples

スポンサーリンク